Release 9400: Some Service Categories fail

This is entirely new in 9400. We upgraded over the weekend and everything "appeared" to go fine. We even tested, but apparently not enough.

We have 11 Service Catalog Categories. Two of them are not used, containing templates we have turned off. Nine are in use. Seven of those nine are just fine, all templates work just fine.

For the remaining two - the last two on the list for what that's worth - NO TEMPLATES WORK. They all fail to create tickets, and the only thing you get is a red "X" with no text attached. It looks like this:

It is unrelated to custom fields, rules or workflow. I tried creating a new template in one of the affected categories with no custom fields, no field and form rules, no workflow . . . and the form still failed. As you can see, the form does in fact submit, it simply fails to generate a ticket.